Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 7 - Trigonometric Identities and Equations - 7.4 Double-Angle and Half-Angle Identities - 7.4 Exercises - Page 693: 24


$=\cos 45=\dfrac {\sqrt {2}}{2}$

Work Step by Step

$1-2\sin ^{2}\alpha =\cos 2\alpha \Rightarrow 1-2\sin ^{2}22\dfrac {1}{2}=\cos \left( 2\times \left( 22\dfrac {1}{2}\right) \right) =\cos 45=\dfrac {\sqrt {2}}{2}$
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